Annealing is a specific process of heat treatment that alters the properties of metal. While there are many different types of heat treatment, annealing is popular because it increases ductability and reduces hardness. In this post, we’ll cover everything you need to know about the process of annealing.
Kloeckner works with a range of heat treatment steel partners to provide our customers with quality parts that match their specifications. We offer turn-key, heat-treated products from our nationwide stock of plate, bar, and sheet inventory.
Annealing is a heat treatment process that is common in manufacturing because it improves the physical and sometimes chemical properties of metal to be both more durable and more workable. When heated during the specific process of annealing, atoms migrate in their crystal lattice and the number of atom dislocations goes down, leading to changes in both ductility and hardness. As the material cools it crystallizes again.
For many alloys, including the most common in manufacturing, carbon steel, the properties of the metal are determined by the size of the crystal grains and the phase composition. Both change during heating and cooling. With knowledge of the crystal grain composition and the phase diagram, annealing as a heat treatment can be used to take the metal from hard to soft, brittle to ductile. As a result, the metal will be more formable, an obviously favorable property in manufacturing.
As already shared, annealing is used to make metal more ductile and less brittle. Here are the three main benefits to annealing:
Most commonly, many types of steel and cast iron are annealed in the manufacturing industry. There are also specific types of aluminum, copper, and brass that can be annealed. While steel is generally cooled to room temperature in still air, copper and brass can also be quenched in water.
There are three main steps in the annealing process:
Metal is composed of a lattice of crystal structures that are known as grains. Sometimes, the structure of the grains themselves cause stress to the metal. During the first phase of the annealing process, called recovery, a furnace or other type of heat source is utilized to raise the temperature of the material to a point that removes internal stresses.
During recrystallization, further heating raises the temperature of the metal to just below its melting point, high enough that the atoms recrystallize, and low enough that it doesn’t melt.
During the grain growth stage, new crystal grains become fully developed as the metal cools that don’t have the metal’s original stress. The final composition–including the ductility and hardness–is determined by the rate of cooling. Once the metal is annealed, there may be final processing like shaping, stamping, or forming.
Most frequently, you’ll find it in:
Unlike annealing, normalizing is the process of increasing hardness. To normalize the metal, you increase the temperature of the material above the austenitic range and then cool it in room temperature air. Austenization means to heat the metal to a temperature at which its crystal structure changes from ferrite to austenite. If you’re looking for a softer, more ductile metal, choose annealing. If you’re looking for a harder, less ductile metal, choose normalizing. Either way, both heat treatments lead to metals with less stress and more machinability.
Kloeckner works with a range of heat treatment steel partners to provide our customers with quality parts that match their specifications. We offer turn-key, heat-treated products from our nationwide stock of plate, bar, and sheet inventory. Please reach out to Kloeckner Louisville or call (678) 259-8800 for your heat treatment needs.
Kloeckner works with a range of heat treatment steel partners to provide our customers with quality parts that match their specifications. We offer turn-key, heat-treated products from our nationwide stock of plate, bar, and sheet inventory.
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